CBF was measured with neutron activated microspheres (Biopal, 15 μm) before initiation of (after all the instruments had been implanted at the time of the initial surgery) and at the end of the repetitive occlusions (when the rats were anesthetized and the chest was open to mimic the conditions of the first measurement) to measure normal zone flows and flow in the developed collaterals. For the first measurement, neutron activated microspheres labelled with Samarium were mixed with fluorescent (FITC) microspheres (Invitrogen, 10 μm) to identify the collateral-dependent region as described below. For the second measurement, Gold labelled microspheres were used. The microspheres (5×105) were injected directly into the LV cavity via the LV apex during LAD occlusion with a 29-gauge insulin syringe over a 10-second period. During the course of the procedures, systemic pressure and heart rate were recorded (386- BIOS, American Megatrends Inc). The heart was excised and fresh LV was sliced along the short axis and observed with a dissecting microscope and fluorescent light source. The collateral-dependent area (ischemic zone, LAD region) was distinguished as the [area without fluorescent microspheres.]

CBF was measured with radioactive microspheres (Perkins Elmer; φ; 15 μm; 95Nb and 103Ru, ≈4.5x105) before initiation of (after all the instruments had been implanted at the time of the initial surgery) and at the end of the repetitive occlusions (when the rats were anesthetized and the chest was open to mimic the conditions of the first measurement) to measure normal zone flows, native collateral flow, and flow in the developed collaterals. For the first measurement, radioactive microspheres were mixed with fluorescent (FITC) microspheres (φ, 10 μm; ≈9x105, Fluoresbrite Yellow Green, Polysciences, Inc) to identify the collateral-dependent region as described below. For the second measurement, the other nuclidelabeled microspheres were used. The microspheres were agitated for 15 minutes, suspended in saline (total volume, 150 μL), and then injected directly into the LV cavity via the LV apex during LAD occlusion with a 29-gauge insulin syringe over a 10-second period. [...] During the course of the procedures, systemic pressure and heart rate were recorded (386- BIOS, American Megatrends Inc).

The heart was excised and fixed in 4% paraformaldehyde solution
overnight. The fixed LV was sliced along the short axis and observed
with a dissecting microscope and fluorescent light source (LT-9800,
Lightools Research). The collateral-dependent area (LAD region)
was distinguished as the area without fluorescent microspheres.